8. Scope of the proposed work item (max 4000 characters) This document specifies procedures for assessment and verification of constancy of performance (AVCP) of Curved and Flat Surface Sliders in relation to their characteristics. Curved and Flat Surface Sliders, which are types of anti-seismic devices, with main functions in accordance with 3.1.1 and 3.1.2, are intended to be used for building and civil engineering construction works. This document comprises the following types of Curved and Flat Surface Sliders: 1. Curved Surface Sliders (CSS, 3.1.1) (spherical and cylindrical) of the following types: a) single curved surface slider, b) double curved surface slider with rigid slider, c) double curved surface slider with articulated slider, d) multiple curved surface slider with rigid slider, e) multiple curved surface slider with articulated slider, and 2. Flat Surface Sliders (FSS, 3.1.2). This document comprises Curved and Flat Surface Sliders with some or all of the following parts: a) backing plates without lightening hollows and without ribs, b) slider without or with hinge, c) mating elements, d) sliding sheets, undimpled or dimpled, without or with lubricant (being in contact with mating element), e) containment rings (for controlling the CSS/FSS kinematics but not limiting the CSS/FSS displacement capacity). This document comprises Curved and Flat Surface Sliders with the following materials: a) for backing plates without hard chromium plating and for sliders: — steel in accordance with EN 10025:2019 (all parts), — cast iron in accordance with ISO 1083:2018, — cast carbon steel in accordance with ISO 14737:2015, or — stainless steel in accordance with EN 10088:2014 (all parts); b) for backing plates with hard chromium plating: — steel grade S355J2(+N) in accordance with EN 10025-2:2019, or — fine grain steel of the same or higher grade in accordance with EN 10025:2019 (all parts); c) for mating elements: — austenitic steel with thickness of at least 2,5 mm in accordance with EN 10088 2:2014, 1.4401 + 2B or 1.4404 +2B, — backing plates with at least 100 µm hard chromium plating in accordance with EN ISO 6158:2018; d) for sliding sheets with and without lubrication: — UHMWPE (Ultra High Molecular Weight Polyethylene), — PTFE (polytetrafluoroethylene) in accordance with EN 1337 2:2004 (Clause 5.2), — fluorpolymer made of claimed PTFE (polytetrafluoroethylene), or — PTFE filled with solid lubricant and reinforcing fibres; e) lubricants in accordance with EN 1337 2:2004 (5.8). This document does not comprise: a) vertical seismic isolation systems, b) CSS/FSS with restrainers limiting their displacement capacity, and c) CSS/FSS with accumulated sliding path less than 1 000 m.